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photosynthetic biofilms

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– O2, H2S and pH microprofiles in biofilm.

Microbial mats undergo daily cycles that are characterized by dramatic changes in oxygen, pH and H2S dynamics. The mats are highly active systems with functional layers of only a few hundred microns. To investigate the dynamics within these layers it is important that measurements in the mat can be performed at high spatial resolution. Unisense microsensors can be made with sensor tips down to 3 µm and they are therefore very suited for studies of active systems.

This is a study example of microprofiling completed in a costal sediment mat collected at Aggersund, Denmark. During the measurements the mat was exposed to varying light intensities or darkness. Microsensors were mounted on a motorized MicroProfiling System, microsensor position was monitored using a dissection microscope and sensor data was logged using SensorTrace PRO.



Screen dump from SensorTrace PRO showing microprofiles of pH (green) and H2S (blue).


The microbial mat was dominated by Cyanobacteria and in light conditions there was a pronounced oxygen production in the photic zone, where a peak in pH was also evident. H2S was found in the anoxic layer below 1200 µm. The marked shifts in dynamics moving from light to dark conditions were captured with the Unisense microsensors. In the dark the H2S production zone moved upwards along with a rapid decline of oxygen production in the microbial mat.



Microsensor profiles of O2, H2S and pH obtained in a photosynthetic biofilm under light and dark conditions.


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